CW FM radar systems are disclosed in the prior art. For example, the Bessel function distribution of the demodulated frequency component distribution and a method for indicating range as a function of the amplitude ratio of two sequentially ordered Bessel functions is disclosed in U.S. Pat. No. 2,453,169 by Varian. Yamauaka, et al, U.S. Pat. No. 3,872,475 discloses a method of ranging depending upon a time delay between equal levels of J.sub.0 and J.sub.1 (Bessel) terms. Other systems in the prior art use wide band FM modulation to accomplish satisfactory system accuracy.
The systems of the prior art are generally complex and therefore expensive and suffer from a lack of accuracy to a great degree.